Theory Update on Electromagnetic Probes II

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Theory Update on Electromagnetic Probes II
Ralf Rapp Cyclotron Institute Physics
Department Texas AM University College
Station, USA CATHIE/TECHQM Workshop BNL
(Upton, NY), 16.12.09
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1.) Intro Probing Strongly Interacting Matter

• Electromagnetic Probes
• penetrating lEM gtgt Rnuc
• Equilibrium
• EM spectral function
• Im PEM(q0,qmB,T)

• ? Information via EM Spectral Function
• degrees of freedom (parton vs. hadron)
• transport properties (EM conductivity,
  susceptibility)
• relation to order parameters (chiral symmetry)
• measure of temperature

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Outline
1.) Introduction 2.) EM Emission Vector
Mesons ? Thermal Rate and Conductivity ?
Chiral Symmetry Breaking ? r and a1 Meson
in Medium 3.) Dilepton Spectra in A-A ?
Thermal Emission at SPS ? The RHIC
Problem 4.) Conclusions
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2.1 Thermal Electromagnetic Emission
EM Current-Current Correlation Function
Thermal Dilepton and Photon Production Rates
Im ?em(M,q)
Im ?em(q0q)
r -meson dominated
ImPem ImDr ImDw /10 ImDf /5
Low Mass
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2.2 Electric Conductivity

• pion gas (chiral pert. theory)
• sem / T 0.01 for T 150-200 MeV

Fernandez-FraileGomez-Nicola 07

• quenched lattice QCD
• sem / T 0.35 for T (1.5-3) Tc

Gupta 04

• soft-photon limit

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2.3 Chiral Symmetry Breaking Hadron Spectrum
Condensates fill QCD vacuum
Axial-/Vector Correlators
Constituent Quark Mass
Data lattice Bowman et al 02 Theory
Instanton Model DiakonovPetrov Shuryak 85
pQCD cont.

• Weinberg Sum Rule(s)

• chiral breaking q2 1 GeV2
• Gellmann-Oakes-Renner
• mp2 fp2 mq 0qq0

-
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2.4 r-Meson in Medium Hadronic Interactions
Chanfray et al, Herrmann et al, RR et al, Koch
et al, Klingl et al, Mosel et al, Eletsky et al,
Ruppert et al, Sasaki et al
Dr (M,qmB ,T) M 2 - mr2 - Srpp - SrB - SrM
-1
r-Propagator
B,a1,K1...
Sp
r
r
SrB,rM
Srpp
Selfenergies
N,p,K
Sp
Constraints decays B,M? rN, rp, ...
scattering pN ? rN, gA,
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2.4.2 r Meson in Cold Nuclear Matter JLab
Nuclear Photo-Production
r
e e-
g A ? ee- X
Eg1.5-3 GeV
g
CLAS/JLab 08
Theoretical Approach
Riek et al 08
in-medium r spectral function
elementary production amplitude

Fe - Ti
r
g
N
M GeV
Mee GeV
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2.6 Axialvector in Medium Dynamical a1(1260)
p

a1 resonance
. . .
Vacuum
r

In Medium
. . .

• in-medium p r propagators
• broadening of p-r scattering
• amplitude

Cabrera,Jido,RocaRR 09
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3.) Dilepton Spectra in A-A
Thermal Dilepton Emission Rate
e e-
g
Im ?em(M,qmB,T)
Im ?em Im Dr
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3.1 Dilepton Rates Hadronic vs. QGP
dRee /dM2 ?d3q f
B(q0T) Im Pem

• Hard-Thermal-Loop Braaten et al 90
• enhanced over Born rate
• Hadronic and QGP rates
• degenerate around Tc
• Quark-Hadron Duality at all M ?!
• (? degenerate axialvector SF!)

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3.2 Dilepton Excess Spectra at SPS
Thermal Emission Spectrum

• average Gr (T150MeV) 350-400 MeV
• ? Gr (TTc) 600 MeV ? mr
• fireball lifetime tFB (6.51) fm/c

van HeesRR 06, Dusling et al 06, Ruppert et
al 07, Bratkovskaya et al 08
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3.2.2 NA60 Data vs. In-Medium Dimuon Rates
Mmm GeV
van Hees RR 07
RR,Wambach et al 99

• acceptance-corrected data directly reflect
  thermal rates!

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3.2.3 NA60 Excess Spectra vs. Theory
CERN Courier Nov. 2009

• Thermal source does very well
• Low-mass enhancement very sensitive to medium
  effects
• Intermediate-mass total agrees, decomposition
  varies

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3.2.4 NA60 Dimuons Sensitivity to QGP and Tc

• vary critical and chemical-freezeout temperature
  (Tfo 130 MeV fix)

EoS-B
EoS-C

• spectral shape robust duality of dilepton
  rate around Tc!
• intermediate mass (Mgt1GeV) QGP vs. hadronic
  depends on Tc

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3.2.5 EM Probes in Central Pb-Au/Pb at SPS
Di-Electrons CERES/NA45
Photons WA98
Turbide et al 03, van HeesRR 07

• consistency of virtualreal photons (same Pem)
• very low-mass di-electrons ? (low-energy) photons

Srivastava et al 05, LiuRR 06
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3.3 Low-Mass Dileptons at RHIC PHENIX
Inclusive Mass Spectrum Centrality
Dependence of Excess

• Successful approach at SPS fails at RHIC
• Excess concentrated - at low mass
• - in
  central collisions
• - at low
  pt (Teff 100 MeV)

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3.3.2 Origin of the Low-Mass Excess in PHENIX?

• Soft QGP Radiation?

- small Teff slope - why not in semi-central? -
generic space-time argument ? ? maximal
emission around Tmax M / 5.5 (for Im Pem
const) Low mass (Mlt1GeV) Tmax lt
200MeV
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3.3.3 Low-Mass Excess from DCC?
Dileptons from a DCC-DCC annihilation
WithamRR 08

• too small
• DCC-thermal to be evaluated

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3.3.4 Comparison of Thermal Emission Calculations
Chiral Reduction Hydro Hadronic
Many-Body Fireball

• Decomposition at M0.5(0.2)GeV Hadronic
  LO-QGP NLO-QGP
• DuslingZahed
  6 (6) 5.5 (2) 10 (25)
• RRvan Hees
  20 (15) 4 (3)
  --

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4.) Conclusions

• Electromagnetic Probes
• - versatile tool (spectral fcts., transport,
  temp., lifetime!)
• Chiral Symmetry Breaking (Restoration)
• - chiral partners r - a1 (degeneracy at Tc)
• Thermal Dilepton Rates
• - melting r toward Tc quark-hadron
  duality?!
• 
  hadron liquid?!
• Dilepton Spectra
• - quantitative agreement at SPS
• - failure at RHIC thus far (QGP not favored
  DCC??)

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2.3.2 Acceptance-Corrected NA60 Spectra
Mmm GeV
Mmm GeV

• more involved at pTgt1.5GeV Drell-Yan,
  primordial/freezeout r ,

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X.) Example for Comprehensive Analysis NA60
Dileptons
Charmonium Flow
Charmonium Production
? thermal medium radiating from around Tc with
melted r , well-bound J/y with large
collectivity